Can anyone give some general comments commercially available toroidal transformers? e.g made by Toroid corp, Avel...which would you recommend? Well it's common to hear that some readily available toroids are......not up to the job? Thanks

Hi Petter thanks for your reply, I've came across an article somewhere in the net stating that the quality of a transformer can be determined by measuring their quiescent current across the secondary....the lower the better which is somewhere in the miliamps range. any comments?

I think this is an oversimplifaction. There are many factors to consider and I doubt anyone can name them all. One thing that you should look for though is completely separate output windings (no center tap allowed -- that means at least 4 wires on secondary side -- 3 is definitely not recommended if you can choose). This allows you to use two bridges and avoid large currents in the center tap (ground).

If you have very large losses, you also get a lot of heat. Losses are probably more a function of field strength and magnetostriction (material choice) than winding technology due to the incredibly high ratio of magnetic properties of iron wrt air. However, winding techniques for minimum leakage do exist -- you cannot wind the toroid perfectly with one wire, one pass going the same "filler" direction -- it just does not work. Tension is also important I guess. How about materials used for isolation? How about metal thickness (core is wound up of a sheet of metal to minimize Eddie core losses. How about geometry of the core (height versus inner/outer radius etc.)

I like potted center units -- some people pot the whole thing to reduce mechanical effects.